The present invention relates to a suspension device of an industrial vehicle and, more particularly, to a suspension device for a reach type forklift.
FIG. 17 illustrates a suspension device for a reach type forklift, which is disclosed in Japanese Unexamined Patent Publication No. 8-164722. FIG. 17 is rear view of a forklift. The suspension device suspends a rear wheel 183 and a caster 184 such that the rear wheel 183 and the caster 184 move vertically relative to the vehicle body. The rear wheel 183 functions as a driving wheel and a steered wheel.
A cab 180 is located at the rear right of the body. An operator stands in the cab 180. A control panel 181 is located in the front of the cab 180. A steering wheel 182 is located to the left of the cab 180. The rear wheel 183 is steered in accordance with manipulation of the steering wheel 182. The rear wheel 183, or the driving wheel, is located to the left of the cab 180. The caster 184 is located below a bottom plate 180a of the cab 180.
The suspension device includes a parallel linkage 188. The parallel linkage 188 includes a support link 191, an upper link 192, a lower link 193 and a caster link 194. The support link 191 includes a horizontal support base 191a and an arm 191b, which extends downward from one end of the support base 191. A drive unit 187 for supporting the driving wheel 183 is attached to the support base 191a. The drive unit 187 includes a drive motor 185 and a gear housing 186. The gear housing 186 has gears for transmitting rotation of the drive motor 185 to the driving wheel 183. The caster 184 is attached to the distal end of the caster link 194.
One end of the upper link 192 is coupled to the vehicle body by a shaft 195. The other end,of the upper link 192 is coupled to the support base 191a by a shaft 197. One end of the lower link 193 is coupled to the lower end of the arm 191b by a shaft 198. The other end of the lower link 193 is coupled to the vehicle body by a shaft 196. The proximal end of the caster link 194 is coupled to the shaft 196. The axes of the shafts 195 to 198 are the vertexes of an imaginary parallelogram.
The shafts 195, 196 are fixed to the vehicle body. In other words, the shafts 195, 196 are fulcrums of the linkage 188. The parallel linkage 188 is moved about the shafts 195, 196 in accordance with the load acting on the driving wheel 183 and the caster 184. The shafts 195, 196 function as fulcrums. As a result, the driving wheel 183 and the caster 184 are moved in opposite directions.
A lift mechanism (not shown) for carrying loads is located in the front portion of the vehicle body. A reach cylinder 110 is located at the lower part of the body in the center of the lateral direction. The reach cylinder 110 moves the lift mechanism forward and-rearward. The reach cylinder 110 extends in the longitudinal direction of the vehicle body and intersects the lower link 193.
The cab 180 is preferably wide for permitting an operator to easily manipulate the forklift (width is the left-right dimension of FIG. 17). However, in the forklift shown in FIG. 17, the arm 191b of the support link 191 is located to the right of the drive unit 187. That is, the arm 191b is located between the drive unit 187 and the cab 180. Accordingly, the width of the cab 180 is reduced by an amount corresponding the size of the arm 191b. 
The width of the vehicle may be increased to increase the width of the cab 180. However, increasing the width of the vehicle hinders loading and unloading in small spaces.
The lower link 193 is located below the bottom plate 180a of the cab 180. The reach cylinder 110 is located below the lower link 193 and is transverse to the lower link 193. Therefore, a relatively large space is required below the bottom plate 180a for the lower link 193 and the reach cylinder 110. To permit the lower link 193 move vertically, space for the lower link 193 to move must be provided. Accordingly, the bottom,plate 180a must be located at a relatively raised position.
However, raising the bottom plate 180a makes it harder for an operator to get on and off the vehicle. Operators frequently get on and off reach type forklifts. The bottom plate 180a, which is raised to a relatively high position, thus lowers efficiency and increases operator fatigue.
Japanese Unexamined Patent Publication No. 8-156544 discloses a suspension device that is similar to the device of FIG. 17. The device of the publication No. 8-156544 does not include a parallel linkage. However, like the device of FIG. 17, elements that form the suspension are located between the cab and the drive unit. Therefore, the width of the cab is limited.
Accordingly, it an objective of the present invention to provide a suspension device that increases the width of the cab of a vehicle without increasing the width of the vehicle body of the vehicle.
Another objective of the present invention is to provide a suspension device that lowers the bottom plate of the cab.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a suspension device for an industrial vehicle is provided. The vehicle has a driving wheel and a coasting wheel, which are laterally spaced apart. The suspension device suspends the driving wheel and the coasting wheel relative to a vehicle body. A cab is located at a side of the vehicle body and above the coasting wheel. The suspension device includes a coasting wheel support, a drive unit, a drive unit support and a coupler. The coasting wheel support supports the coasting wheel such that the coasting wheel moves upward and downward relative to the vehicle body. The driving wheel is attached to the drive unit. The drive unit support supports the drive unit such that the drive unit moves upward and downward relative to the vehicle body. The coupler is located in the vehicle body. The drive unit support is coupled to the coupler such that the drive unit support moves relative to the vehicle body. The coupler is located at a position other than a position that is lateral of the drive unit.
The present invention provides another suspension device for an industrial vehicle. The vehicle has a driving wheel and a coasting wheel, which are laterally spaced apart. The suspension device suspends the driving wheel and the coasting wheel relative to a vehicle body. The suspension device includes a coasting wheel support, a drive unit, a drive unit support and an interlock mechanism. The coasting wheel support supports the coasting wheel such that the coasting wheel moves upward and downward relative to the vehicle body. The driving wheel is attached to the drive unit. The drive unit support supports the drive unit such that the drive unit moves upward and downward relative to the vehicle body. The interlock mechanism interlocks the drive unit support with the coasting wheel support such that the driving wheel and the coasting wheel move in opposite directions. The interlock mechanism includes a rotatable shaft that extends in the lateral direction of the vehicle body. Load acting on the driving wheel and load acting on the coasting wheel are applied to the shaft as opposing torsional forces. The shaft rotates such that the torsion applied to the shaft by the driving wheel and the torsion applied to the shaft by the coasting wheel are balanced, and the driving wheel and the coasting wheel move in opposite directions.
The present invention further provides another suspension device for an industrial vehicle. The vehicle has a driving wheel and a coasting wheel, which are laterally spaced apart. The suspension device suspends the driving wheel and the coasting wheel relative to a vehicle body. The vehicle includes a cab located at a side of the vehicle body and above the coasting wheel. The vehicle also includes a carrier for carrying a load and an actuator for moving the carrier forward and rearward. The suspension device includes a coasting wheel support, a drive unit, a drive unit support and an interlock mechanism. The coasting wheel support supports the coasting wheel such that the coasting wheel moves upward and downward relative to the vehicle body. The driving wheel is attached to the drive unit. The drive unit support supports the drive unit such that the drive unit moves upward and downward relative to the vehicle body. The interlock mechanism interlocks the drive unit support with the coasting wheel support such that the driving wheel and the coasting wheel move in opposite directions. The interlock mechanism crosses the actuator at a location that is forward or rearward of the cab.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.